CN112832053A

CN112832053A - Method for controlling the thickness of a parent-roll fibre web and production line for producing a fibre web

Info

Publication number: CN112832053A
Application number: CN202011322148.9A
Authority: CN
Inventors: 亚科·哈帕宁
Original assignee: Valmet Technologies Oy
Current assignee: Valmet Technologies Oy
Priority date: 2019-11-22
Filing date: 2020-11-23
Publication date: 2021-05-25
Anticipated expiration: 2040-11-23
Also published as: FI129063B; US12006176B2; FI20196003A1; EP3825267A1; CN112832053B; EP3825267B1; US20210155436A1

Abstract

The invention relates to a method for controlling the thickness of a fiber web W of a parent roll produced in a fiber web production line, which fiber web production line comprises: a headbox (11); a molding section (12); a press section (13); a drying section (14); a calender (15); an application section (16); a winder (18) for winding the parent roll; an unwinding table (21) of the slitter-winder; a slitting part of the slitting rewinder; and a winding section (22) of the slitter-winder for winding the customer rolls. Before winding the fiber web W onto a parent roll in a winder (18), the thickness of the fiber web W is controlled according to the diameter of the parent roll or the diameter of the customer roll.

Description

Method for controlling the thickness of a parent-roll fibre web and production line for producing a fibre web

Technical Field

The present invention relates generally to the production of fibrous webs, and more particularly to the production of board webs (board webs). More specifically, the invention relates to a method for controlling the thickness (caliper) of a fiber web of a parent roll according to the preamble of the independent method claim and to a manufacturing line for producing a fiber web according to the preamble of the independent manufacturing line claim.

Background

As is known from the prior art, a fiber web production process usually comprises an assembly formed by a plurality of apparatuses arranged one after the other on a production line. A typical production and processing line includes a headbox, a wire section and a press section, as well as a subsequent dryer section and winder. The production and processing line may also comprise other parts and devices for finishing the fibrous web, such as size press, coating device and calender. The production and processing line also typically includes at least one slitter-winder for forming customer rolls and a roll wrapping apparatus. As is known, a fiber web (such as a paper or board web) is continuously manufactured in machines forming a fiber web production line, which may be up to several hundred meters long.

In a fiber web manufacturing line, the production run is a continuous process, and the process is typically run at a constant speed and constant basis weight when producing a selected fiber web grade. The completed fibrous web output from the machine is wound around a winding shaft (i.e., a winding roll) with a winder to form a parent roll (machine reel). The parent roll may be greater than 5 meters in diameter and may weigh more than 160 tons. The purpose of the winding is to convert the fiber web from its planar manufactured form to a form that can be handled more easily. A winder is thus a device that winds material, which is produced as a continuous fibre web in a fibre web production line, into the form of a reel, i.e. a parent roll. In the production of fiber webs, winding is usually the first process part, in which a continuous process is broken off to continue sequentially. The parent rolls are formed around winding shafts that serve as winding cores, i.e. the fibre web on one parent roll around one winding shaft has a starting point and an end point.

The parent roll is wound tight enough to withstand winding, storage (including roll transfer) and subsequent unwinding. Generally, the goal is to have the tightness of the parent roll decrease or at least remain unchanged from the inner layer to the surface. It is known from the prior art to define the real-time parent or reel thickness and density by means of a measurement and calculation system. It is also known to define a roll-in thickness (wind-in caliper) curve during winding. One known system is described in patent application publication WO02102693a 1. The winding parameters (compression load, web tension and circumferential force) are determined based on, for example: paper or board properties (e.g., smoothness, stiffness, compressibility, and coefficient of friction), parent roll size, processing method, storage time, and running speed. The winding parameters are usually only changed when the fibre web grade changes or there is a winding problem.

The web of the parent roll produced in the manufacturing process is full-width, even greater than 100 km long, and must therefore be cut into partial webs of suitable width and length for the customer before being distributed from the factory and wound on a core to form a "customer roll". As is known, such slitting and winding of the web material is carried out in a separate machine suitable for the purpose, i.e. a slitter-winder. In slitter-winders, a parent roll is unwound from a winding shaft in an unwinding table and a wide web is slit with a slitting section into a number of narrower partial webs which are wound around a winding roll (e.g. a core) by a winding section in the winder to form customer rolls. When the customer rolls are ready, the slitter-winder is stopped and the rolls (or "packs") are removed from the machine. Thereafter, the process will continue with the winding of a new group. These phases are repeated periodically until the fibre web on the parent roll is exhausted from the winding shaft, at which point the parent roll is replaced and the operation is restarted to unwind a new parent roll from the winding shaft.

Fiber webs (especially paper and board) are of various types and can be classified into two grades according to basis weight: a single layer and a basis weight of 25 to 300 grams per square meter (g/m)²) The paper of (1); and is produced by a single-layer or multi-layer technique and has a basis weight of 150 to 600g/m²The plate of (1). It should be noted that the boundary between paper and board is flexible, with the board grade having the lightest basis weight being lighter than the heaviest paper grade. Generally, paper is used for printing and board is used for packaging. The major carton board grades are Folding Box Board (FBB), white lined chip board (WLC), solid bleached board (SBS) and Liquid Packaging Board (LPB). Generally, these grades are commonly used for different types of consumer product packaging. The grade of the paperboard for the box ranges from single-layer paperboard to five-layer paperboard (150-400 g/m)²) Are not equal. The top surface is usually coated with one to three layers (20-40 g/m)²) While the back side has less coating orNot coated at all.

Bulk (i.e. the thickness of the fibrous web versus the grammage (basis weight) of its board web) is reduced during winding and the loss of thickness due to stresses inside the parent roll is usually greatest in the inner layers of the parent roll. In addition, some volume losses may occur during winding in the slitter-winder. For these reasons, in board manufacturing, board webs are usually produced with thickness values exceeding a target value (even 5%) in order to reach the target value even in the worst case. Thus, during production time, even more than 90% of the time runs with thickness values that exceed the target value. This also has a significant economic negative investment. These disadvantages and problems increase as the bulk of the fibrous web increases.

In publication EP2107997a 1a method is disclosed for winding a continuous web material to form a substantially fully compressed roll of wound web material, so that the machine direction tension in the web material is substantially uniform throughout the wound roll of web material. In the method, a compensated WOT profile is generated and varies with the diameter of the winding drum, and as the web material is wound onto the drum, the compensated WOT profile is the WOT required in the web material to provide the winding drum with a substantially uniform through-drum MD tension. In the method, the compensated WOT curve can be converted to a speed control based on a predetermined relationship between the rewinding machine speed and the WOT of the web.

It is an object of the present invention to create a method for controlling the thickness of a fiber web of a parent roll and a production line for producing a fiber web, wherein the disadvantages and problems of the prior art are eliminated or at least minimized.

A particular object of the present invention is to create a method for controlling the thickness of a fiber web and a production line for producing a fiber web, wherein the following disadvantages and problems of the prior art are eliminated or at least minimized: the fibrous web is produced with a thickness value exceeding the target value.

Disclosure of Invention

In order to achieve the object defined above, the method for controlling the thickness of a fiber web according to the invention is primarily characterized by the features of the characterizing part of the independent method claim, and the manufacturing line for producing a fiber web according to the invention is primarily characterized by the features of the characterizing part of the independent manufacturing line claim. Advantageous embodiments and features are disclosed in the dependent claims.

In the present description and claims, the expression "inner layer of the parent roll" means 10%, advantageously 5% of the total length of the fibre web on the parent roll.

According to the invention, in a method for controlling the thickness of a fiber web of a parent roll produced in a fiber web production line comprising a headbox, a forming section, a press section, a drying section, a calender, a coating section, a winder, a unwinding table of a slitter-winder, a slitting section of a slitter-winder, a winding section of a slitter-winder, the thickness of the fiber web of the parent roll is controlled depending on the diameter of the parent roll.

According to an advantageous feature of the invention, in the method, at least one of the following operating parameters of the production line is adjusted to wind the parent roll: web speed (i.e., production speed), headbox flow, headbox consistency, coating weight of the coating stock, and/or calender press load to control the thickness of the fibrous web.

According to an advantageous feature of the invention, in the method, the thickness of the fibre web to be wound as the inner layer of the parent roll is adjusted to exceed a set target value for the thickness of the fibre web by adjusting the operating parameters.

According to an advantageous feature of the invention, in the method the completed parent roll is provided with a fibrous web having a desired thickness (advantageously, a constant thickness) according to the parent roll or the customer roll.

According to an advantageous feature of the invention, the adjustment of the operational parameters is started at the latest when the fibre web is to be wound into the innermost layer of the parent roll and continues for a time interval corresponding to the winding of the inner layer of the parent roll. According to an advantageous aspect, it is preferred that the run during the change of parameter is timed to correspond to the time of running the bottom or surface scrap layer of the parent roll.

According to an advantageous feature of the invention, the running speed of the production line is reduced in order to provide a fibre web having a thickness value exceeding the target value for the thickness of the fibre web of the inner layer of the parent roll.

According to an advantageous feature of the invention, a fibrous web is provided having a thickness value exceeding the target value of the thickness of the fibrous web of the inner layer of the parent roll by increasing the headbox flow and/or by increasing the headbox consistency and/or by increasing the coating weight of the coating stock and/or by reducing the calender press load.

According to an advantageous feature of the invention, the time interval for running with the adjusted operating parameters for running the inner layer of the parent roll is advantageously defined by thickness data calculated on the basis of data received from an on-line measuring device (advantageously a sensor) at the unwinding station of the slitter-winder and/or from an on-line measuring device (advantageously a sensor) at the winding of the slitter-winder. The thickness data may be calculated based on known calculation systems, for example, as described in patent application publication WO02102693a 1.

According to an advantageous feature of the invention, the fiber web is produced in a fiber web production line, which fiber web production line further comprises a parent roll store with sample collecting stations and/or a customer roll store with sample collecting stations, and the time interval for running with the adjusted running parameters for running the inner layers of the parent roll is advantageously defined by the thickness measurement data received from the sample collecting stations.

According to an advantageous feature of the invention, the method comprises:

a target setting step, in which target thickness data of the fiber web are set;

a parameter selection step, in which the operating parameters are selected and defined: web speed (i.e. production speed), headbox flow and/or headbox consistency, coating weight of coating stock to be applied on the fiber web at the coating section and calender press load of the calender to produce a fiber web with a target thickness;

a measuring step, wherein thickness data is received;

a checking step, in which it is checked on the basis of the received thickness data whether the thickness of the fibre web according to the diameter of the parent roll or the customer roll is desired, advantageously the thickness of the fibre web is constant in the parent/customer roll, and if the thickness of the fibre web in the parent/customer roll is not desired (advantageously not constant), a return branch is selected, and in the factor change step the diameter-dependent correction factor is changed, and in the parameter selection step the selected operating parameter is changed accordingly.

According to an advantageous feature of the invention, the method further comprises: a sample measuring step, wherein thickness data are received, followed by a sample checking step, and it is checked, based on the thickness data received from the sample measuring step, whether the thickness of the fibre web according to the diameter of the parent roll or the customer roll is desired (advantageously, the thickness of the fibre web in the parent roll/in the customer roll is constant), and if the thickness of the fibre web in the parent roll/in the customer roll is not desired (advantageously, not constant), an additional return branch is selected, and in the factor changing step the diameter-dependent correction factor is changed, and in the parameter selecting step the selected operating parameters are changed accordingly.

According to the invention, a production line for producing a fiber web comprises: a head box; a molding section; a press section; a drying section; a calender; a coating section; a winding machine; an unwinding table of the slitting rewinder; a slitting part of the slitting rewinder; the winding section of the slitter-winder and measuring means, e.g. sensors, advantageously an on-line measuring device for measuring the fibre web of the parent roll to calculate the thickness of the fibre web to be unwound in the unwinding station and/or to define the thickness of the fibre web to be wound to the client roll in the winding station, e.g. on the basis of a known calculation system, e.g. a system as described in patent application publication WO02102693a1, wherein the production line further comprises a database and calculation means for collecting and storing the measurement data received from the measuring means and calculating, e.g. as described in patent application publication WO02102693a1, and determining the thickness profile of the parent roll as a function of the diameter of the parent roll and calculating the thickness as output data from the diameter of the parent roll/client roll, which output data are sent as input data to the control means of the fibre web production line, to adjust at least one of the following operating parameters of the production line to wind the parent roll: web speed (i.e., production speed), headbox flow, headbox consistency, coating weight of the coating stock, and/or calender press load to control the thickness of the fibrous web.

According to an advantageous feature of the invention, the production line further comprises a parent roll store and a sample collecting station at the parent roll store and/or a customer roll store and a sample collecting station at the customer roll store for collecting samples of the fiber web to define the thickness of the fiber web.

According to an advantageous aspect of the invention, the thickness of the fibre web is controlled upon unwinding at the unwinding station of the slitter-winder according to the diameter of the parent rolls, alternatively or additionally according to the diameter of the group of customer rolls. Advantageously, the thickness is increased before winding in the winder (changing to a new parent roll for winding) and the thickness increased for a set time is wound as the inner layer of the parent roll. After that, the thickness is set to a target value. Thus, at unwinding, the thickness of the unwound fibrous web has a desired thickness (advantageously a constant thickness) according to the diameter of the parent roll/the thickness of the fibrous web to be unwound from the customer roll has a desired thickness (advantageously a constant thickness) according to the diameter of the customer roll. Advantageously, the run time of the increased thickness is about 10% of the winding of one parent roll in the winder.

According to an advantageous aspect of the invention, the thickness of the fibre web is adjusted by reducing the production speed of the production line, typically 2-3% (even up to 10%, if required), based on the thickness profile of the parent roll being unwound in the unwinding station of the slitter-winder, so that the fibre web to be wound as an inner layer of the parent roll will have an increased thickness to compensate for the volume loss of winding and spooling.

According to another advantageous aspect of the invention, the thickness of the fibre web is adjusted by reducing the production speed of the production line, typically 2-3% (even up to 10% if required), based on the thickness profile of the customer reel set produced in the slitter-winder, so that the fibre web to be wound as an inner layer of the parent reel will have an increased thickness to compensate for the volume loss of winding and spooling.

Alternatively, in order to provide increased thickness to the inner layer of the parent roll, the headbox consistency and/or flow at the slice of the headbox is adjusted accordingly for the inner layer of the parent roll. In the case of the production of a multi-layer fiber web, for example, only the consistency of the middle layer headbox and/or the flow at the slice of the middle layer headbox is adjusted.

Alternatively, in order to provide an increased thickness to the inner layer of the parent roll, the coating weight of the coating slip to be applied to the fibre web at the coating section is adjusted accordingly for the inner layer of the parent roll.

Alternatively, in order to provide an increased thickness to the inner layer of the parent roll, the calender nip load is adjusted accordingly for the inner layer of the parent roll.

By means of the invention and its advantageous features, a number of advantages are achieved: the amount of consumed raw material and the consumed energy is reduced by a few percent and the target value of the produced fibre web is still achieved. Thus, significant environmental and economic savings are also realized.

Drawings

Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

An advantageous example of a fibre web production line according to the invention is schematically shown in fig. 1.

A schematic example of a flow chart illustrating the steps of a method for controlling the thickness of a fibre web of a parent roll is shown in fig. 2.

Exemplary thickness loss curves are schematically illustrated in fig. 3A and 3B, wherein fig. 3A illustrates a thickness loss curve according to the prior art and fig. 3B illustrates a thickness loss curve according to the present invention.

A portion of one thickness run of the parent roll is schematically illustrated in fig. 4A and 4B, where fig. 4A illustrates the thickness run according to the prior art and fig. 4B illustrates the thickness run according to the present invention.

In the course of the following description, like numerals and symbols will be used to identify like elements, in accordance with the various views illustrating the invention and advantageous examples thereof. In the drawings, some repetitive reference numerals have been omitted for clarity.

Detailed Description

In fig. 1 is very schematically shown a fibre web production line comprising a headbox 11, a forming section 12, a press section 13, a drying section 14, a calender 15, an application section 16 with a drying device 17, a winding machine 18, a parent roll store 19, an unwinding table 21 of a slitter-winder, a slitting section (not shown) of the slitter-winder, a winding section 22 of the slitter-winder and a customer roll store 23, and a packaging section 24. There are also guide rolls 10, 20 in the production line for guiding and supporting the fibrous web W and/or for guiding and supporting the fabric F for supporting the web W. The fibrous web W is typically supported by a fabric during forming, pressing and drying. The production line comprises a measuring device 31, such as a sensor, advantageously an in-line measuring device, with a computing system to measure and calculate (as described in patent application publication WO02102693a 1) the thickness of the fibrous web W, for example of a parent roll to be unwound in the unwinding station 21 and/or the thickness of the fibrous web defined in the winding section 22 to be wound onto a customer roll. The production line may further comprise a sample collecting station 32 at the parent roll store 19 and/or at the customer roll store 23 for collecting samples of the fiber web in order to define the thickness of the fiber web W. The production line further comprises a database and calculation means 33 for collecting and storing thickness data received from the measuring means with a calculation system and/or information received from the sample collection station and calculating and determining a thickness profile of the parent roll and/or calculating the thickness from the diameter of the parent/customer roll as output data. This output data is sent as input data to the control device 34 of the fiber web manufacturing line to control the production speed of the fiber web manufacturing line such that the production speed during winding of the inner layers of the parent roll in the winder 18 is decreased to temporarily increase the thickness and bulk of the inner layers of the parent roll to provide the parent roll of fiber web with a desired target thickness (advantageously constant) according to the diameter of the parent roll to be unwound in the unwinding station 21 of the slitter-winder.

A schematic example is shown in fig. 2, which is a flow chart illustrating the steps of a method for controlling the thickness of a fiber web of a parent roll. Each fiber web grade has a grade-based correction factor. In a target setting step 41 of the method, target thickness data of the fiber web are set. Then, in a parameter selection step 42, the operating parameters of the fiber web manufacturing line (web speed (i.e. production speed), headbox flow and/or headbox consistency, coating weight of the coating stock to be applied to the fiber web at the coating section and/or calender press load of the calender) are selected and defined to produce a fiber web with a target thickness. In a measuring step 43, thickness data (advantageously calculated based on online calculation results received by the calculation system from the parent roll at the unwinding section of the slitter-winder) is received. Then, in a checking step 44, it is checked on the basis of the received thickness data whether the thickness of the fibre web is as desired based on the diameter of the parent roll/customer roll, advantageously the thickness of the fibre web is constant in the parent roll/in the customer roll. If the thickness of the fibre web in the parent roll is not as desired based on the diameter of the parent/customer roll (advantageously, not constant), the return branch 51 is selected (i.e. "no") and the diameter-dependent correction factor is changed in the factor change step 45 and the selected operating parameter is changed accordingly in the parameter selection step 42. Additionally (or alternatively), in a sample measurement step 46, thickness data (advantageously calculated based on-line thickness data received from the sample acquisition station) is received. Then, in a sample checking step 47, it is checked, based on the thickness data received from the sample measuring step 46, whether the thickness of the fibre web is, as desired, based on the diameter of the parent/customer roll, advantageously the thickness of the fibre web is constant in the parent/customer roll. If the thickness of the fibre web in the parent roll is not as desired (advantageously constant), the additional return branch 52 is selected (i.e. "no"). Furthermore, the diameter-dependent correction factor is changed in a factor change step 45, and the selected operating parameter is changed accordingly in a parameter selection step 42. In case the thickness is based as desired on the diameter of the parent/customer roll (advantageously constant in the parent roll), the continuation branch 53 is selected (i.e. "yes") and production is continued with the set parameters.

According to an advantageous example of the invention, which is explained herein with reference to the example of fig. 1-2, the thickness of the fibre web W of the parent roll is controlled in the method according to the diameter of the parent roll. In the method, the parent roll is wound by adjusting at least one of the following operating parameters of the production line: the web speed (i.e. the production speed), the headbox flow, the headbox consistency, the coating weight of the coating stock and/or the calender press load are such that the thickness of the fibre web W to be wound as the inner layer of the parent roll exceeds a target value and a desired thickness according to the diameter of the parent roll/customer roll, a constant thickness of the fibre web of the parent roll is advantageously achieved. Thus, the parameters are adjusted starting when the fibre web W is to be wound into the innermost layer of the parent roll and continuing for a time interval corresponding to the winding of the inner layer of the parent roll. Advantageously, the running speed of the production line is reduced so that the fibrous web W runs at an "excess thickness" (i.e. a thickness value exceeding the target value for the thickness of the fibrous web W of the inner layer of the parent roll). And, the "over thickness" run is achieved by increasing the headbox flow, increasing the headbox consistency, increasing the coating weight of the coating stock, and/or by reducing the calender press load. Advantageously, the time interval required for the "excess thickness" run of the inner layer of the parent roll is defined by measurement data received from an on-line measuring device 31 (advantageously a sensor), which on-line measuring device 31 has a computing system located at the unwinding table 21 of the slitter-winder. Additionally or alternatively, the time interval required for the "over thickness" run of the inner layer of the parent roll is defined by measurement data received from an on-line measuring device 31 (advantageously a sensor) with a computing system at the winding section 22 of the slitter-winder and/or thickness measurement data received from a sample collection station 32 at the parent roll store 19 and/or the customer roll store 23.

Exemplary thickness loss curves are schematically illustrated in fig. 3A and 3B, wherein a thickness loss curve according to the prior art is illustrated in fig. 3A and a thickness loss curve according to the present invention is illustrated in fig. 3B. The diameter of the parent roll is shown in millimeters (mm) in the X-axis and the thickness is shown in micrometers (μm) in the Y-axis. In fig. 3A and 3B, curves 61A, 61B represent the thickness of the fibre web before the winding stage in the winder, curves 62A, 62B represent the thickness of the fibre web in the parent roll, curves 63A, 63B represent the thickness of the fibre web in the winding stage in the winding section of the slitter-winder, and curves 64A, 64B represent the target value of the thickness of the fibre web. In the reference numerals, the letter a denotes a value realized by the prior art, and the letter B denotes a value realized by the present invention. As can be seen from fig. 3A in the prior art system, the difference between the target value 64A of the thickness and the thicknesses 61A-63A used is large, but as can be seen from fig. 3B of the present invention, the range of the difference between the target value 64B of the thickness and the thicknesses 61B-63B used is much smaller, and the difference between the desired target values (i.e., curves 64A, 64B) of the prior art and the present invention is large, so the situation has been significantly improved.

The over-thickness run portion of the parent roll is schematically illustrated in fig. 4A-4B, the over-thickness run portion according to the prior art is illustrated in fig. 4A, and the over-thickness run portion according to the present invention is illustrated in fig. 4B. As can be seen from prior art fig. 4A, the run time of the excess thickness is about 90% of the run time of the unwinding parent roll, but in the present invention, as can be seen from fig. 4B, the run time of the excess thickness is only about 10% of the run time of the unwinding parent roll, and the situation has been significantly improved.

Curves

65A, 65B show the change in diameter of the parent roll over time, and the

coverage areas

66A, 66B show portions of excess thickness travel.

In the foregoing description, although some functions have been described with reference to certain features and examples, those functions may be performed by other features and examples, whether described or not. Although features have been described with reference to certain examples, those features may also be present in other examples, whether described or not.

The above describes only some advantageous examples of the invention, to which the invention is not limited, and within which many modifications and variations are possible.

Claims

1. A method for controlling the thickness of a fiber web W of a parent roll produced in a fiber web production line, which fiber web production line comprises: a headbox (11); a molding section (12); a press section (13); a drying section (14); a calender (15); an application section (16); a winder (18) for winding the parent roll; an unwinding table (21) of the slitter-winder; a slitting part of the slitting rewinder; a winding part (22) of the slitter-winder for winding customer rolls, characterized in that,

-controlling the thickness of the fibre web W according to the diameter of the parent roll or according to the diameter of the customer roll before winding the fibre web W onto the parent roll in the winder (18).

2. Method according to claim 1, characterized in that in the method at least one of the following operating parameters of the production line is adjusted for winding the parent roll for controlling the thickness of the fibre web: web speed, headbox flow, headbox consistency, coating weight of the coating stock, and/or calender press load.

3. A method according to claim 2, characterised in that the web speed is a production speed.

4. A method according to claim 1 or 2, characterised in that, in the method, the thickness of the fibre web W to be wound as the inner layer of the parent roll is adjusted to exceed a set target value for the thickness of the fibre web by adjusting the operating parameters.

5. Method according to any of claims 1 or 2, characterized in that in the method the completed parent roll is provided with a fibre web having a desired thickness according to the diameter of the parent roll.

6. Method according to claim 5, characterized in that the completed parent roll is provided with a fibre web having a constant thickness.

7. Method according to claim 2, characterized in that the adjustment of the operating parameters is started at the latest when the fibre web W is to be wound into the innermost layer of the parent roll and for a time interval corresponding to the winding of the inner layer of the parent roll.

8. Method according to claim 2, characterized in that the running speed of the production line is reduced in order to provide a fibre web W having a thickness value exceeding the target value for the thickness of the fibre web W of the inner layer of the parent roll.

9. Method according to claim 2, characterized in that a fibrous web W having a thickness value exceeding the target value for the thickness of the fibrous web W of the inner layer of the parent roll is provided by increasing the headbox flow, and/or by increasing the headbox consistency, and/or by increasing the coating weight of the coating stock, and/or by reducing the calender press load.

10. The method of claim 2, wherein the time interval for operating with the adjusted operating parameters for operating the inner layer of the parent roll is defined by thickness data received from: -an on-line measuring device (31) with a computing system located at the unwinding station (21) of the slitter-winder.

11. The method according to claim 10, characterized in that the online measuring device (31) is a sensor.

12. The method of claim 2, wherein the time interval for operating with the adjusted operating parameters for operating the inner layer of the parent roll is defined by thickness data received from: -an on-line measuring device (31) with a computing system located in the winding section (22) of the slitter-winder.

13. The method according to claim 12, characterized in that the online measuring device (31) is a sensor.

14. A method according to claim 2, characterised in that the fibre web manufacturing line further comprises a parent roll store (19) with a sample collecting station (32) and/or a customer roll store (23) with a sample collecting station (32) and is run at time intervals with adjusted running parameters for running the inner layers of the parent rolls defined by the thickness measurement data received from the sample collecting station (32).

15. The method according to claim 1 or 2, characterized in that the method comprises:

a target setting step (41) in which target thickness data of the fiber web are set;

a parameter selection step (42) in which the following operating parameters are selected and defined: a web speed, a headbox flow and/or a headbox consistency, a coating weight of a coating stock to be applied on the fiber web at the coating section and a calender press load of the calender to produce a fiber web having a target thickness;

a measuring step (43) in which the thickness data is received;

a checking step (44) in which it is checked on the basis of the received thickness data whether the thickness of the fibre web according to the diameter of the parent roll or the customer roll is desired, and if the thickness of the fibre web in the parent roll or the customer roll is not desired, a return branch (51) is selected, and in a factor changing step (45) the diameter-dependent correction factor is changed, and in the parameter selection step (42) the selected operating parameter is changed accordingly.

16. The method of claim 15, wherein the web speed is a production speed.

17. Method according to claim 15, characterized in that the thickness of the fibre web is constant in the parent roll or in the customer roll.

18. The method according to any one of claims 1 or 2, further comprising:

-a sample measuring step (46) in which thickness data are received, and then-a sample checking step (47) in which it is checked, on the basis of the thickness data received from the sample measuring step (46), whether the thickness of the fibre web according to the diameter of the parent roll or the customer roll is desired, and if the thickness of the fibre web in the parent roll or the customer roll is not desired, an additional return branch (52) is selected, and-in the factor changing step (45) a diameter-dependent correction factor is changed, and-in the parameter selection step (42) the selected operating parameter is changed accordingly.

19. Method according to claim 18, characterized in that the thickness of the fibre web is constant in the parent roll or in the customer roll.

20. A production line for producing a fibrous web, the production line comprising: a headbox (11); a molding section (12); a press section (13); a drying section (14); a calender (15); an application section (16); a winder (18) for winding the parent roll; the unwinding platform (21) of the slitting rewinder is used for winding the client roll; a slitting part of the slitting rewinder; -a winding section (22) of the slitter-winder and-a measuring device (31), the measuring device (31) having a computing system and being adapted to define a thickness of a fibre web W of a parent roll to be unwound in the unwinding station (21) and/or to define a thickness of a fibre web to be wound in the winding section (22) to a customer roll, characterized in that the production line further comprises: -database and calculation means (33) for collecting and storing thickness data received from the measuring means and calculating and determining a parent roll thickness profile as a function of the diameter of the parent roll, for calculating the thickness according to the diameter of the parent roll or the customer roll as output data, which output data is sent as input data to control means (34) of the fiber web manufacturing line for adjusting at least one of the following operational parameters of the manufacturing line for winding the parent roll: web speed, headbox flow, headbox consistency, coating weight of the coating stock and/or calender press load to control the thickness of the fibrous web.

21. The production line of claim 20, wherein the measuring device (31) is an in-line measuring device.

22. The production line of claim 21, characterized in that the measuring device (31) is a sensor.

23. A production line according to claim 20, characterised in that the web speed is a production speed.

24. A production line according to claim 20, characterized in that the production line further comprises a parent roll store (19) and a sample collecting station (32) at the parent roll store (19) and/or a customer roll store (23) and a sample collecting station (32) at the customer roll store (23) for collecting samples of the fibre web to define the thickness of the fibre web W.